A variety of equilibrium techniques are being used to probe the binding site for pyridoxal 5'-phosphate with various enzymes. These techniques include nuclear magnetic resonance, equilibrium binding studies, studies of coenzyme analogs, and chemical modification. A variety of kinetic techniques are being used to probe interactions among enzyme, coenzyme, and substrate. These techniques include steady-state kinetics, studies of substrate analogs, chemical modification by substrate-analog inhibitors, isotope effects, and other such techniques. Particularly study is being made of abortive transaminations occurring during reactions of amino acid ecarboxylases.